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technical article
Several problems encountered with multi-point thermocouples
2012-2-18 11:32:25


Main technical parameters of multi-point thermocouple

公称压力:一般是指在工作温度下保护管所能承受的静态外压而破裂。 Multi-point thermocouple nominal pressure: Generally refers to the static external pressure that the protection tube can withstand at operating temperature and rupture. Minimum insertion depth of thermocouple: should not be less than 8-10 times the outer diameter of its protective sleeve (except for special products) Insulation resistance: When the ambient air temperature is 15-35 ° C and the relative humidity is <80%, the insulation resistance is ≥5 trillion European (voltage 100V). Thermocouple with splash-proof junction box. When the relative temperature is 93 ± 3 ℃, the insulation resistance is ≥0.5 Megohm (voltage 100V). The insulation resistance at high temperature: the thermocouple at high temperature, its thermal electrode (including double branch type) ) The insulation resistance (per meter) between the protective tube and the two hot electrodes should be greater than the value specified in the table below. A point thermocouple is a temperature sensing element that converts a temperature signal into a thermoelectromotive force signal and an electrical meter into the temperature of the measured medium. The basic principle of thermocouple temperature measurement is that two homogeneous conductors of different components form a closed loop. When there is a temperature gradient at both ends, a current will pass through the loop. At this time, there is a Seebeck electromotive force between the two ends. Electromotive force, this is the so-called Seebeck effect. Multi-point thermocouples are suitable for production sites where the temperature gradient is not significant, and multiple locations or a single location must be measured simultaneously. Multi-point thermocouples are widely used in large fertilizer synthesis towers, storage tanks and other devices.

遇到的几个问题: Several problems encountered with multipoint thermocouples :
1. The thermoelectric potential of the thermocouple is a function of the temperature difference between the two ends of the thermocouple's working end, not the function of the temperature difference between the cold end and the working end of the thermocouple; 2. The size of the thermoelectric potential generated by the thermocouple, when the thermoelectric When the material of the thermocouple is uniform, it has nothing to do with the length and diameter of the thermocouple, but only with the composition of the thermocouple material and the temperature difference between the two ends. 3. When the composition of the two thermocouple wire materials of the thermocouple is determined, The size is only related to the temperature difference of the thermocouple; if the temperature of the cold end of the thermocouple is kept constant, the thermoelectric potential of the incoming thermocouple is only a single value function of the temperature of the working end. Multipoint thermocouples measure temperature. When using it, you must pay attention to the following points: 1. The cold junction constant temperature or cold junction temperature compensation of the multi-point thermocouple. 2. The connecting wire of the multi-point thermocouple to the instrument must use the compensation lead with the same index number as the thermocouple. 3. The division number of the multi-point thermocouple and the measuring instrument must be the same.


特性及用途:针对水泥干法旋窑生产线有关三级筒、四级筒、五级筒锥体温度,分解炉中部、窑尾烟、窑头罩温度的测温特点,因普通耐磨热电偶因保护管材质题目,无法满足耐高温、耐冲洗的特种测温条件,导致热电偶使用寿命较短、条件经费加大、产品更换频繁、传输信号得不到保障、仪表长期处于警戒状态,同时给仪表维护增加了不少的工作量,这种现象是目前全国水泥行业所存在的普遍性题目。 Multi-point thermocouple characteristics and uses: According to the temperature characteristics of the three-level, four-level, and five-level cones of the cement dry rotary kiln production line, the temperature measurement characteristics of the temperature in the middle of the decomposition furnace, the tail smoke of the kiln, and the hood of the kiln are common. Due to the problem of the material of the protective tube, the wear-resistant thermocouple cannot meet the special temperature measurement conditions of high temperature resistance and flushing resistance, which results in a shorter service life of the thermocouple, increased condition funding, frequent product replacement, unreliable transmission signals, and long-term instrumentation. The state of alert, while adding a lot of workload to instrument maintenance, this phenomenon is a common problem existing in the national cement industry.
Over the years, the Dongxiang Group has conducted a number of researches and studies on the material of thermocouple bushings that are resistant to high temperatures and flushing. Based on the characteristics of foreign cement production processes, after many experiments and online use, the NM recrystallized thermocouple has a service life. Long, good shock performance, high thermal conductivity, oxidation resistance, thermal shock resistance, high temperature resistance, corrosion resistance, flush resistance, no nodulation, no slagging, convenient installation and use, etc. It can be used for special measurement of 600 ~ 1200 ℃ Temperature occasions cannot be replaced by thermocouple protection tubes made of corundum, high alumina, graphite, silicon oxide silicon carbide and other materials in China. The advent of the NM alloy steel protection tube thermocouple not only solves a major difficulty in the wear-resistant temperature measurement control of the Chinese cement industry, but also brings considerable economic benefits to various users.

Product features: Professionally designed and developed temperature measuring instrument. High precision and long service life. Good shock performance and high thermal conductivity.
Resistant to oxidation and corrosion. Resistance to thermal shock and high temperature. No nodules and slagging. 4 to 8 mm wall thickness. Fast response function, strong stability. Any optional protective tube length. Can be used without preheating. Various installation methods suitable for each user. Optional in-place display. Optional built-in transmitter function. Anti-interference ability during long interval transmission. Wide range of ambient temperature, stable and reliable operation.